McCook engineers were especially interested in flying higher, faster, and farther. On February 27, 1920, Major Rudolph "Shorty" Schroeder set a solo altitude record of 33,114 feet in a supercharged open cockpit Packard-LePere LUSAC-11 two-place biplane. His achievement proved that the aircraft could withstand the high altitude; but the pilot could not tolerate the low temperature and thin air. When Major Schroeder landed at McCook Field after the record-breaking flight, his eyelids were frozen open. Such experiences provided impetus for engineers in the Equipment Laboratory to design protective flight clothing and improved equipment. Those early tests eventually led to the development of closed cockpits, heated cabins, and eventually, pressurized cabins. Schroeder recovered from this February flight and went on to make numerous high-altitude flights, earning him the nickname "the Icicle King."
When Lieutenant James H. Doolittle pushed the Engineering Division's XCO-5 beyond 37,000 feet in 1925, he temporarily lost consciousness in the thin oxygen and -70 degree Fahrenheit temperature. Fortunately, he revived enough to land the aircraft safely at McCook Field and report his experience to engineers, who, in time, went on to design improved oxygen systems, including tanks, meters, masks, and non-frosting goggles.